28p 



JOURNAL OF CONCHOLOGY. 



Vol. 15. SEPTEMBER, 1918. No. 10. 



THE PISIDIUM FAUNA OF THE GRAND JUNCTION 

 CANAL IN HERTS. AND BUCKS. 



Jv A. W. STELFOX, M.R.I. A. 



(Read before the Society, January gth, igiS). 



Plates 7, 8, and 9. 



The opinions expressed in the following paper regarding the identity 

 of some of the shells are put forward tentatively, and yet with confi- 

 dence ; tentatively because they differ in some cases fundamentally 

 from those in the most recently published work on the British Fistdia{\); 

 with confidence because the available evidence supports them. This 

 evidence is based on the study of much material, in addition to that 

 dealt with in this paper, which has been supplied by the kindness of 

 several correspondents, who not only sent me the specimens already 

 in their collections, but also specially collected material, which they 

 forwarded to me alive for examination. To these correspondents I 

 am deeply indebted, and I tender them my thanks. 



The paper deals with the species of the genus Pisiditim which are 

 found in that portion of the Grand Junction Canal — a stretch of 

 approximately nine miles — which crosses the chalk range of the 

 Chilterns between Berkhamsted in Hertfordshire and Cheddington in 

 Buckinghamshire, and attains at the highest point an altitude of 

 nearly 400 feet. The origin of the present paper may be traced to 

 the finding of Pisidiuni parvultim in sand dredged from the rivers 

 Barrow, Suir, and Shannon in Ireland (4). 



In the early months of 1916, Mr. Phillips and I were in need of 

 young examples of P. snpiniim for comparison with our Irish speci- 

 mens of P. parvidum, and I wrote to Mr. Charles Oldham asking 

 him to collect P. supinuin of all ages, and suggested that he should 

 at the same time look out for P. parvuluin, as some shells in my 

 possession from the Pleistocene deposits at Grays, Essex, were, in our 



Numbers in brackets refer to works mentioned in the Bibliography at the end. 



